Swift: Hold code execution until API response received - swift

Question

I need to set up authorization screen:
1) Login and pass is inputted
2) App requests token from API
3) Response is received
4) App checks if response contains token: if contains, should perform authorization
PROBLEM TO SOLVE: app makes 4) before step 3)
What I tried: I used escaping closure in order to hold the execution until API data is received, but it helped only partially - it helped to hold only assignment of value to token, but I cannot hold 'if checks' still.
override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
if identifier == "loginSegue" {
let login = loginInput.text!
let password = passInput.text!
tokenLoader.getToken(login: login, password: password) { [weak self] token in
self?.token = token.access_token
}
//THIS CODE I NEED TO HOLD UNTIL DATA FROM API RECEIVED
if token != "" {
return true
} else {
let alert = UIAlertController(title: nil, message: "Incorrect password", preferredStyle: .alert)
let action = UIAlertAction(title: "OK", style: .cancel, handler: nil)
alert.addAction(action)
present(alert, animated: true, completion: nil)
return false
}
//
} else {
return true
}
}
class TokenLoader {
let session = Session.instance
let baseUrl = "http://46.254.18.193:9096"
func getToken(login: String, password: String, completion: #escaping (AccessToken) -> Void) {
let path = "/token"
let parameters: Parameters = [
"grant_type": "client_credentials",
"client_id": login,
"client_secret": password,
"scope": "read"
]
let url = baseUrl+path
AF.request(url, method: .get, parameters: parameters).responseData { response in
do {
let token = try JSONDecoder().decode(AccessToken.self, from: response.value!)
print(token)
self.session.token = token.access_token
completion(token)
} catch {
print(error)
}
}
}
}

Answer 1

You can resolve the issue using this function ... perform it on event when you want to segue or to get token
func getTokenAndPerformSegue() {
let login = loginInput.text
let password = passInput.text
if let getLogin = login ,let getPassword = password {
tokenLoader.getToken(login: getLogin, password: getPassword) { [weak self] token in
self?.token = token.access_token
if token.isEmpty() {
let alert = UIAlertController(title: nil, message: "Incorrect password", preferredStyle: .alert)
let action = UIAlertAction(title: "OK", style: .cancel, handler: nil)
alert.addAction(action)
present(alert, animated: true, completion: nil)
} else {
performSegue(withIdentifier: "loginSegue", sender: nil)
}
}
}
}
you need to write it like this ... to return nil or error in completion
func getToken(login: String, password: String, completion: #escaping (AccessToken?) -> Void) {
let path = "/token"
let parameters: Parameters = [
"grant_type": "client_credentials",
"client_id": login,
"client_secret": password,
"scope": "read"
]
let url = baseUrl+path
AF.request(url, method: .get, parameters: parameters).responseData { response in
do {
let token = try JSONDecoder().decode(AccessToken.self, from: response.value!)
print(token)
self.session.token = token.access_token
completion(token)
} catch {
completion(nil)
print(error)
}
}
}
Let me know if you did not get anything or you need further help